This invention relates to systems and methods for indicating the location of structural members, such as pre-tensioned and post tensioned cable, strands and rods, which are disposed within the interstices of concrete members.
Many concrete members, such as concrete slabs or beams, employ high-strength structural members as the means of pre-tensioning or post-tensioning these members for providing strength requirements. In the building construction industry a serious safety concern is posed if these post-tension members are damaged or severed when holes used for anchorage devices or utility lines are drilled into the slab after the concrete has hardened. More specifically, since these tension members are the primary source of strength, these concrete members may fail if the tension members are severed.
The present methods of locating structural members are limited to the use of x-ray photography and/or magnetic induction devices. However, the x-ray photography and magnetic induction devices cannot distinguish between the mild standard concrete steel of concrete reinforcing elements and that of the structural members, respectively. Therefore, severing of the structural members often results. Moreover, the more reliable x-ray photography requires evacuation of the area being exposed during location of structural members for safety reasons.
With respect to other non-analogous uses such as underground utility lines in U.S. Pat. No. 3,523,515 and U.S. Pat. No. 3,927,637, devices have been provided which indicate the depth below ground depth and/or water level of those utility lines. In these devices, the depth can be read by an observer at the ground and/or water level surface.
Therefore, a need exists for a system for easily and accurately indicating the location of structural members located in the interstices of concrete members, in order to avoid the unwanted severing of these structural members when for example, holes are drilled into the concrete member.